1. Field
Disclosed herein is a method for the production of magnetic powder composite cores pressed from a mix of alloy powder and binder. Also disclosed is a magnet core produced from a mix of alloy powder and binder and an inductive component containing such a magnet core.
2. Description of Related Art
In powder composite cores of this type, low hysteresis and eddy-current losses and low coercitive field strength are desired. The powder is typically supplied in the form of flakes provided by comminuting a soft magnetic strip produced using melt spinning technology. These flakes may, for example, have the form of platelets and are typically first provided with an electrically insulating coating and then pressed to produce a magnet core. While flakes of pure iron or iron/nickel alloys are so ductile that they are plastically deformed under the influence of the compacting pressure and result in pressed cores of high density and strength, flakes or powders of relatively hard and rigid materials cannot be pressed with just any pressure. Rigid flakes would break in unsuitable conditions, resulting not in the desired compaction, but only in a further reduction of particle size. In addition, the break-up of the flakes releases fresh surfaces without any electrically insulating coating, which can lead to a drastic reduction of the resistivity of the magnet core and thus to high eddy-current losses at high frequencies.
As described, for example, in DE 103 48 810 A1, it is possible to use powders with a multi-modal particle size distribution. A multi-modal size distribution permits a relatively dense packing of the particles, and thus permits the production of a relatively dense magnet core.
When using FeAlSi-based materials, the high energy input required for comminution results in structural damage in the production of fine-grain particle fractions, but such damage is healed virtually completely in the subsequent heat treatment process and hardly affects the magnetic properties of the finished magnet core. In mixes with ductile materials, packing density can be increased by increasing the ductile component, for example the pure iron component. This procedure is, for example, described in JP 2001-196216.